When ichthyosaurs were alive, some of the dolphin-like sea creatures may have had dark-colored skin covering their entire bodies.

Many ocean-dwelling animals are darker on their upward-facing side and lighter on their underside. But chemical analyses of dark traces in fossilized tissue show that a 190-million- to 196-million-year-old ichthyosaur had skin pigments that made the animal uniformly dark, researchers suggest January 8 in Nature.

The team also found skin pigments, including melanin, in fossil tissue of a 55-million-year-old leatherback turtle and an 86-million-year-old mosasaur. The results help scientists understand how skin pigments may have helped animals live in colder parts of the world and expands the understanding of coloration in extinct animals beyond fossilized feathers.